and stationary smooth density \(\rho = \rho _0(x_2,\dots ,x_n)\) . In this case the velocity component \(u\)  satisfies a fractional parabolic equation which will be shown to fulfill the assumptions of known regularity results in [1]}, [2]} that give uniform Schauder bounds on \(u\)  in class \(C^{1+\gamma }\) . Hence, the criterion applies, see Section REF .
